1. Field of the Invention
The present invention relates to a method of preparing an image of a special color separation other than Y, M, C, and K separations, with respect to a color image reproduced by a plurality of color separations including at least Y, M, and C separations, and also to an apparatus for the same.
2. Description of the Related Art
In ordinary color image printing, the four basic color inks of Y (yellow), M (magenta), C (cyan), and K (black) are used. Y, M, and C are three primary colors of additive mixture of color stimuli. In simplified printing, color images are occasionally printed with only the three primary colors of Y, M, and C. In order to enhance the color reproducibility, ink of a special color other than Y, M, C, and K is used for some printing. Such ink of a special color is generally referred to as `special color ink`, and a color separation of the special color ink is referred to as `special color separation`. Typical examples of special color ink include green, orange, gold, silver, and other metallic colors. The special color separation is generally used for reproducing an image part for which a special color has been designated in advance, such as a logotype, or for enhancing the color reproducibility of a color image by printing in special color ink.
Color images have conventionally been expressed by image data of four color separations, Y, M, C, and K. In order to generate image data of a special color separation from the image data of Y, M, C, and K separations, the user is required to specify an image area of the special color separation and the densities of the respective color separations including the special color separation in the specified image area.
Further, the conventional method of generating a special color separation usually converts the densities of the color separations in a specific image area, such as a vignette image area (gradation image area), to the density of the special color separation even when the conversion to the special color separation is not desired in the specific area.